buglist: bug 7271: Mistake in an example from book introduction

in section 0.2.2, "Type Conversion" of Axiom Book, there's an
example of a conversion that seems to be wrong. It uses

(4.6)::Float

Since there's no point in a coercion from Float to a Float, from
the context, it seems the intention was to write:

(23/5)::Float